On computers, it has now become commonplace for advertisements (often called banner or pop-up ads) to appear (usually uninvited) on user's screens from time to time. These advertisements sometimes include video and are intended to promote products and services relevant to the user. With the introduction of smart phones, tablets and pads, the challenge to provide timely, meaningful and effective advertising has become more difficult.
One problem is that there is a large size difference between devices. Pop-up advertising must be designed to display properly on the relatively small screen of a cell phone as well as on the much larger display of an iPad. Compounding the problem is that at any given moment the user's display can be in either landscape or portrait mode. On a relatively square display space the orientation of the device is not a concern. This is not so on large rectangular displays.
Another problem is that the advertisement itself often overlaps the viewing area the user is focused on. In such a situation, it is imperative that the pop-up ad disappear from view relatively quickly to avoid alienating the user. Removing the ad faster than the user can absorb its contents makes no sense. However, allowing the ad to obscure what the user is primarily interested in is counterproductive.